Technical Field
The present disclosure pertains to the field of lighting devices and, more specifically, proposes an add-on Visible Light Communication (VLC) controller for a light-emitting diode (LED) lighting device.
Description of Related Art
Visible Lighting Communication, a subset of optical wireless communication technologies, is a data communication using visible light between 400 and 800 THz (780-375 nm). The technology transmits data by adjusting the intensity or the on-off cycle of the visible light. Popular Light Intensity Baseband Modulation (LIBM) includes On-Off Keying (OOK), Pulse Amplitude Modulation (PAM), and Pulse Position Modulation (PPM). The first general of VLC device achieved 10 kbit/s data transmission rate by using fluorescent lamp. Recently LED light source was used and this dramatically improved the VLC data rate up to 500 Mbit/s.
FIG. 1 depicts schematically a typical LED-based VLC system where the VLC controller comprises of a protocol engine for interpreting the incoming data stream and a transceiver for converting the incoming data into LIBM modulated signal stream. The LIBM modulated signal stream is fed to the LED driver which in turn drives the LED diode to emit VLC encoded data by adjusting the light intensity at a frequency higher than human eye can perceive. On the VLC signal receiving end, there is a photo diode for receiving the VLC data, and the received data is fed to the VLC transceiver for demodulation, and then the VLC protocol engine for interpretation. The VLC receiving device is typically a smartphone or a specially designed electronic device.
VLC has several advantages over traditional wireless communication technologies. First of all, its spectrum is license-free. Secondly, it is free of RF health concerns. Thirdly, it has the potential of delivering ubiquitous computing since light-producing devices as such lamps (indoor/outdoor), TVs, traffic signs, street light, car headlights/taillights, and commercial displays are everywhere. VLC data communication is more secure since data can only be received where the VLC light source is visible. It is also less susceptible to RF-noise. Lastly, the high data rate offered by LED light source makes it very cost-effective for delivering large of amount of data over a short distance.
The conventional approach of designing a VLC-enabled LED lighting devices is to embed the VLC controller inside an integrated LED device as shown in FIG. 1. This approach has the advantage of achieving the maximal controllability of the LED device by the VLC controller. It however severely limits the deployment of the VLC technology, because firstly it requires existing LED lighting devices to be replaced with VLC-enabled ones, which could induce significant costs on material and labor for replacement. Secondly, once a VLC controller is embedded inside of an LED lighting device, it can't be upgraded or improved easily. Given the long life of LED lighting device of 10-20 years, it is foreseeable that the VLC technology would make significant improvement over this time span on data transmission speed and functionality. An embedded VLC controller design would prevent the user from taking the advantage of the latest and more cost-effective VLC technology. The present disclosure overcomes the above limitations of embedded VLC controller design by extending and applying the invention of “Add-on Smart Controller for LED Lighting Device” in U.S. Pat. No. 9,089,031 to VLC controller.